The present invention relates to a filter element comprising a tubular folded bellows or bag of folded filter material.
Filter elements of this type are utilized to filter air or also liquids, whereby the medium to be filtered passes through the filter material into the interior of the filter element and there is conveyed away, whereby the dirt particle load is collected on the filter material.
From U.S. Pat. No. 2,556,521 a round filter element is known in which a cylindrical filter material is compacted in the longitudinal direction of the cylinder and a filter bag is thereby formed. The compacted fold-blades of the folded bag thereby increase the effective filter surface of the filter element. At the axial ends of the filter element, the fold-blades form a flat flange surface on which plate-form closure covers are attached, which enclose the margins and seal off the interior of the folded bag. One of the closure covers is penetrated by a clean air duct. The clean air duct has a perforated construction and extends through the folded bag in the axial direction up to the opposite axial end. The entire filter element is inserted in a housing which has a connecting nipple for supplying the medium to be filtered, which is filtered by passing through the folded bag and reaches the interior of the clean air duct through the perforations.
From DE 27 25 437 A1 a round filter element with a radially profiled folded bag for cleaning dust-containing air is known in which at the axial ends of the folded bag is folded a flat flange projection onto which flat-surfaced end pieces with un-profiled surfaces are applied.
In many applications it is advantageous to be able to construct a filter element which is curved with respect to its longitudinal dimension in order to be able to use it in ducts having a correspondingly curved construction.